linux-kernel - Re: [cpuops inc_return V1 6/9] Taskstats: Use this_cpu

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Message-ID: <alpine.DEB.2.00.1012070844350.25976@router.home>
Date:	Tue, 7 Dec 2010 08:45:12 -0600 (CST)
From:	Christoph Lameter <cl@...ux.com>
To:	Michael Holzheu <holzheu@...ux.vnet.ibm.com>
cc:	Tejun Heo <tj@...nel.org>, akpm@...ux-foundation.org,
	Pekka Enberg <penberg@...helsinki.fi>,
	linux-kernel@...r.kernel.org,
	Eric Dumazet <eric.dumazet@...il.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>
Subject: Re: [cpuops inc_return V1 6/9] Taskstats: Use this_cpu_ops


On Tue, 7 Dec 2010, Michael Holzheu wrote:

> I think this is wrong and should be:
>
> -	listeners = &__raw_get_cpu_var(listener_array);
> +	listeners = __this_cpu_ptr(>>>> & <<< listener_array);
>

Correct. CONFIG_TASKSTATS was not set. Thus



Subject: Taskstats: Use this_cpu_ops

Use this_cpu_inc_return in one place and avoid ugly __raw_get_cpu in another.

V3->V4:
	- Fix off by one.

V4-V4f:
	- Use &listener_array

Cc: Michael Holzheu <holzheu@...ux.vnet.ibm.com>
Signed-off-by: Christoph Lameter <cl@...ux.com>

---
 kernel/taskstats.c |    5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

Index: linux-2.6/kernel/taskstats.c
===================================================================
--- linux-2.6.orig/kernel/taskstats.c	2010-12-06 11:30:01.000000000 -0600
+++ linux-2.6/kernel/taskstats.c	2010-12-07 08:43:32.000000000 -0600
@@ -89,8 +89,7 @@ static int prepare_reply(struct genl_inf
 		return -ENOMEM;

 	if (!info) {
-		int seq = get_cpu_var(taskstats_seqnum)++;
-		put_cpu_var(taskstats_seqnum);
+		int seq = this_cpu_inc_return(taskstats_seqnum) - 1;

 		reply = genlmsg_put(skb, 0, seq, &family, 0, cmd);
 	} else
@@ -581,7 +580,7 @@ void taskstats_exit(struct task_struct *
 		fill_tgid_exit(tsk);
 	}

-	listeners = &__raw_get_cpu_var(listener_array);
+	listeners = __this_cpu_ptr(&listener_array);
 	if (list_empty(&listeners->list))
 		return;

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